EP0981629B1 - Forms of prostate specific antigen and methods for their detection - Google Patents

Forms of prostate specific antigen and methods for their detection Download PDF

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EP0981629B1
EP0981629B1 EP98918814A EP98918814A EP0981629B1 EP 0981629 B1 EP0981629 B1 EP 0981629B1 EP 98918814 A EP98918814 A EP 98918814A EP 98918814 A EP98918814 A EP 98918814A EP 0981629 B1 EP0981629 B1 EP 0981629B1
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ppsa
psa
antibody
antibodies
sample
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English (en)
French (fr)
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EP0981629A1 (en
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Mohammad S. Saedi
Stephen D. Mikolajczyk
Abhay Kumar
Lana S. Grauer
Robert L. Wolfert
Harry G. Rittenhouse
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Hybritech Inc
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Hybritech Inc
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/14—Hydrolases (3)
    • C12N9/48—Hydrolases (3) acting on peptide bonds (3.4)
    • C12N9/50—Proteinases, e.g. Endopeptidases (3.4.21-3.4.25)
    • C12N9/64—Proteinases, e.g. Endopeptidases (3.4.21-3.4.25) derived from animal tissue
    • C12N9/6421—Proteinases, e.g. Endopeptidases (3.4.21-3.4.25) derived from animal tissue from mammals
    • C12N9/6424—Serine endopeptidases (3.4.21)
    • C12N9/6445—Kallikreins (3.4.21.34; 3.4.21.35)
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C07K16/40—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against enzymes

Definitions

  • the present invention relates generally to the detection and identification of proteins, as well as various forms and subunits of proteins, which have potential utility as diagnostic markers.
  • the present invention relates to the detection of inactive precursor forms of prostate specific antigen.
  • Prostate cancer is the most frequently diagnosed cancer in American males. Parker, S.L. et al., CA Cancer J. Clin., 46:5-27, 1996 .
  • Prostate specific antigen, or PSA has been widely used as a reliable prognostic marker in the management of patients with prostate cancer.
  • Catalona W.J. et al., N. Engl. J. Med., 324:1156-1161, 1991 ; Oesterling, J.E., J. Urol., 145:907-923, 1991 ; Labrie, F. et al., J. Urol., 147:846-852, 1992 .
  • PSA also known as hK3
  • hK3 a member of human kallikrein family of serine proteases
  • aa 261 amino acid preproprotein in which a hydrophilic signal sequence of 17 aa (prepro region) and a propeptide of 7 aa precedes the mature protein of 237 aa. Lundwall, A.
  • PSA mRNA expression is predominant in prostate epithelium, Qui, S. et al., J. Urol. 144:1550-1556, 1990 , and is regulated by androgens, Young, C.Y.F. et al., Cancer Res., 51:3748-3752, 1991 .
  • PSA has been shown to have chymotrypsin-like activity.
  • the proposed primary biological role of PSA is to cleave the major gel forming proteins, semenogelin I, II and fibronectin in seminal fluid, resulting in enhanced sperm motility. Lilja, H., J. Clin. Invest., 76:1899-1903, 1985 .
  • PSA has been reported to cleave the IGF binding protein 3, resulting in increased IGF activity, a function that may be important in regulation of epithelial cell growth in the prostate.
  • the fundamental questions regarding its biosynthesis, activation and regulation of activity remain unanswered.
  • the human kallikrein family consists of three members designated as hK1, hK2 and hK3 (PSA). Clements, J.A., Endocr. Rev., 10:393-419, 1989 ; Carbini, L.A. et al., J. Hypertens., 11:893-898, 1993 . hK1 is primarily produced in the kidney, pancreas and submandibular salivary gland. Fukushima, D. et al., Biochemistry, 24:8037-8043, 1985 . hK2, like PSA. is produced predominantly in the prostate epithelium ( Morris, B.J., Clin. Exp. Pharm.
  • PSA is a chymotrypsin-like protease whereas hK2 is a trypsin-like protease, Mikolajczyk, S.D. et al., Human glandular kallikrein (hK2) shows arginine-restricted specificity and forms complexes with plasma protease inhibitors, Prostate 34:44-50, 1998 indicating that the two enzymes have different physiological roles. Little is known about the physiological role(s) of hK2. Deperthes et al. have recently shown that fibronectin present in ejaculate was hydrolyzed more efficiently by hK2 than by PSA ( J. Androl., 17: 659-665, 1996 ). On the other hand, semenogelins were hydrolyzed by hK2 to a similar extent as that of PSA. While PSA and hK2 have been shown to be present in the same environment, their interaction with each other has not been studied.
  • An expression vector is described herein which clones and stably expresses PSA in mammalian cells. It is herein demonstrated for the first time that PSA is secreted into the spent media by mammalian cells as proPSA. The proPSA thus secreted is enzymatically inactive and stable in the media. It is also demonstrated that proPSA can be converted to enzymatically active PSA in the extracellular medium by hK2. This suggests a possible physiological relationship between hK2 and PSA and that hK2 could be regulating PSA activity in vivo.
  • a chimeric expression vector comprising a nucleic acid molecule.
  • the nucleic acid molecule encodes a pPSA polypeptide.
  • the nucleic acid molecule is preferably operably linked to control sequences which are recognized by a host cell that is transformed with the expression vector.
  • the host cell is preferably derived from a mammalian source.
  • the present invention provides a method for detecting proPSA in a human physiological fluid
  • this aspect of the invention is based on the discovery that proPSA exists in biological fluid and may serve as a useful marker for prostate cancer.
  • proPSA exists in biological fluid and may serve as a useful marker for prostate cancer.
  • several inactive precursor forms of PSA have been identified and at least one has been detected in serum.
  • the measurement of these inactive precursor forms of PSA may provide important information regarding the diagnosis and staging of prostate cancer.
  • proPSA polypeptides as well as variants and subunits thereof, produced by the methods of the present invention can be used to produce populations of antibodies that, in turn, can be used as the basis for direct or competitive assays to detect and quantify proPSA polypeptides (or "protein") in samples derived from physiological fluids, such as seminal fluid, blood or serum, tissues, such as prostate carcinomas, or cells, such as prostate cells.
  • physiological fluids such as seminal fluid, blood or serum
  • tissues such as prostate carcinomas, or cells, such as prostate cells.
  • Another embodiment of the present invention therefore, provides an antibody, and preferably a monoclonal antibody, which specifically binds to proPSA.
  • Such antibodies specifically bind to the various inactive precursor forms of proPSA, including [-1]pPSA, [-2]pPSA, [-[-3]pPSA, [-4]pPSA, [-5]pPSA, [-6]pPSA and [-7]pPSA.
  • Hybridoma cell lines producing such antibodies are also provided by way of the present invention.
  • a method for detecting proPSA in a sample of human physiological fluid includes providing purified antibodies to pPSA, contacting the antibodies with the sample to allow formation of complexes between the antibodies and pPSA, and determining the presence or amount of pPSA complexed with the antibodies. Diagnostic methods and kits are also included as embodiments of the present invention.
  • inactive precursor forms of PSA in serum suggests that measuring serum concentrations of proPSA can be useful in the diagnosing and monitoring of prostate cancer.
  • expression of PSA in mammalian cells is necessary.
  • PSA PSA polypeptide
  • PSA polypeptide PSA polypeptide
  • proPSA proPSA polypeptide
  • proPSA polypeptide PSA polypeptide
  • pPSA polypeptide PSA polypeptide
  • chimeric means that a vector comprises DNA from at least two different species, or comprises DNA from the same species, which is linked or associated in a manner which does not occur in the "native" or wild type of the species.
  • Control sequences is defined to mean DNA sequences necessary for the expression of an operably linked coding sequence in a particular host organism.
  • the control sequences that are suitable for prokaryotic cells include a promoter, and optionally an operator sequence, and a ribosome binding site.
  • Eukaryotic cells are known to utilize promoters, polyadenylation signals and enhancers.
  • operably linked means that the nucleic acids are placed in a functional relationship with another nucleic acid sequence.
  • DNA for a presequence or secretory leader is operably linked to DNA for a polypeptide if it is expressed as a preprotein that participates in the secretion of the polypeptide;
  • a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to facilitate translation.
  • "operably linked” means that the DNA sequences being linked are contiguous and, in the case of a secretory leader, contiguous and in reading phase. However, enhancers do not have to be contiguous. Linking is accomplished by ligation at convenient restriction sites. If such sites do not exist, the synthetic oligonucleotide adaptors or linkers are used in accord with conventional practice.
  • the recombinant DNA can be readily introduced into the target cells by transfection with an expression vector comprising cDNA encoding PSA, for example, by the modified calcium phosphate precipitation procedure of C. Chen et al., Mol. Cell. Biol., 7, 2745 (1987 ). Transfection can also be accomplished by lipofection, using commercially available kits, e.g., provided by Life Technologies, Inc. (Gibco BRL), Rockville, MD USA.
  • Suitable host cells for the expression of PSA are derived from multicellular organisms. Such host cells are capable of complex processing and glycosylation activities.
  • mammalian cells are the preferred host for expression of mammalian protein since these cells modify and process the recombinant protein in a manner closely related to the natural host of the protein.
  • any higher eukaryotic cell culture can be employed in the practice of the invention, whether from vertebrate or invertebrate culture.
  • invertebrate cells include plant and insect cells. Numerous baculoviral strains and variants and corresponding permissive insect host cells have been identified.
  • PCR Polymerase chain reaction
  • RNA and/or DNA are amplified as described in U.S. Patent No. 4,683,195 .
  • sequence information from the ends of the region of interest or beyond is employed to design oligonucleotide primers. These primers will be identical or similar in sequence to opposite strands of the template to be amplified.
  • PCR can be used to amplify specific RNA sequences, specific DNA sequences from total genomic DNA, and cDNA transcribed from total cellular RNA, bacteriophage or plasmid sequences, and the like. See generally Mullis et al., Cold Spring Harbor Symp. Quant. Biol., 51, 263 (1987 ); Erlich, ed., PCR Technology, (Stockton Press, NY, 1989 ).
  • PSA polypeptide When PSA polypeptide is expressed in a recombinant cell other than one of human origin, the PSA polypeptide is completely free of proteins or polypeptides of human origin. However, it is necessary to purify PSA polypeptide from recombinant cell proteins or polypeptides to obtain preparations that are substantially homogeneous as to PSA polypeptide. For example, the culture medium or lysate can be centrifuged to remove particulate cell debris. The membrane and soluble protein fractions are then separated. The PSA polypeptide may then be purified from the soluble protein fraction, and if necessary, from the membrane fraction of the culture lysate.
  • PSA polypeptide can then be purified from contaminant soluble proteins and polypeptides by fractionation on immunoaffinity or ion exchange columns; ethanol precipitation; reverse phase HPLC; chromatography on silica or on an anion exchange resin such as DEAE; chromatofocusing; SDS-PAGE; ammonium sulfate precipitation; gel filtration using, for example, Sephadex G-75; or ligand affinity chromatography.
  • a proPSA polypeptide or peptide corresponding to the proPSA region can be used to produce anti-pPSA antibodies.
  • the proPSA polypeptides used to generate antibodies in accordance with the invention include, but are not limited to -7, -5 and -4 proPSA.
  • Peptides corresponding to the proPSA region can also be used to generate anti-pPSA antibodies and include all peptides which contain any portion of the pro region of the pPSA polypeptide. These peptides preferably contain about 8 to 15 amino acids and comprise an immunogenic epitope.
  • Monoclonal antibodies against purified pPSA (total protein) or the above peptides can be prepared using known hybridoma cell culture techniques, for example, as described by E. Harlow et al., Antibodies: A laboratory manual, Cold Spring Harbor Laboratory. 1988 .
  • this method involves preparing an antibody-producing fused cell line, e.g., of primary spleen cells fused with a compatible continuous line of myeloma cells, and growing the fused cells either in mass culture or in an animal species from which the myeloma cell line used was derived or is compatible.
  • Such antibodies offer many advantages in comparison to those produced by inoculation of animals, as they are highly specific and sensitive and relatively "pure" immunochemically.
  • Immunologically active fragments of antibodies are also within the scope of the present invention, e.g., the F(ab) fragment, as are partially humanized monoclonal antibodies.
  • the isolated pPSA polypeptide produced in accordance with a method of the present invention and its antigenically active variants, derivatives and fragments thereof can be used in assays for proPSA in samples derived from biological materials suspected of containing proPSA or anti-proPSA antibodies.
  • a two-antibody sandwich technique can be used primarily to determine the antigen concentration in unknown samples.
  • Two-antibody assays are quick and accurate, and if a source of pure antigen, in this case proPSA, is available, the assays can be used to determine the absolute amounts of antigen in unknown samples.
  • the assay requires two antibodies that bind to non-overlapping epitopes on the antigen. Either two monoclonal antibodies that recognize discrete sites or one batch of affinity-purified polyclonal antibodies can be used.
  • one antibody is purified and bound to a solid phase. Any solid phase can be used, however, for most applications, a PVC microtiter plate is preferred.
  • the antibody bound for example to a well of a microtiter plate, is unlabelled and is referred to as the "capture antibody.”
  • the amount of antibody to be used will depend on the individual assay, but an amount of about 1 ⁇ g/well generally gives maximal binding. Higher or lower amounts of capture antibody can also be used.
  • the wells can then be washed and sample added to the wells to allow the antigen, in this case pPSA, in the test solution to bind to the solid phase. Unbound proteins can be removed by washing, and a labeled second antibody can be added.
  • the sample and the second labeled antibody can be added simultaneously.
  • the assay can be quantitated by measuring the amount of labeled second antibody that is bound to the solid phase.
  • a most preferred embodiment of the present invention utilizes a monoclonal antibody as the first unlabeled antibody and a monoclonal antibody as the second labeled antibody.
  • the detection method used to quantitate the amount of bound labeled antibody depends on the label used.
  • Antibodies can be labeled conveniently with iodine, enzymes or biotin. Calorimetric or other detection methods can be used.
  • the proPSA polypeptides of the present invention can be immobilized and used as "capture antigens" to bind and immobilize anti-pPSA antibodies from a sample to be assayed for anti-pPSA antibodies.
  • the bivalent complex of proPSA polypeptides and anti-pPSA antibodies is then detected, e.g., in the case of human physiological material, by reacting it with an anti-human IgG antibody which comprises a detectable label or a binding site for a detectable label. In the latter case, the binding site is itself reacted with a compound specific for the binding site, which itself comprises a detectable label.
  • Useful detectable labels include enzymes, radiolabels or fluorescent labels.
  • the resultant ternary or quaternary complex can then be detected and/or quantified via the detectable label, i.e., via an enzyme-substrate color-forming reaction, radioemission, agglomeration, and the like.
  • the proPSA polypeptide can be labeled with a detectable label, such as via one or more radiolabeled peptidyl residues, and can be used to compete with endogenous proPSA for binding to anti-proPSA antibodies, i.e., as a capture antigen to bind to anti-proPSA antibodies in a sample of a physiological fluid, via various competitive immunoassay formats.
  • a competitive immunoassay for detecting or determining proPSA in a sample of human physiological fluid containing pPSA comprises:
  • the immunoassays as described in detail above can be used in a method to detect pPSA in human physiological samples, such as serum and tissue, for the purpose of diagnosing and monitoring prostate cancer.
  • the assays of the present invention can also be used in a method to distinguish prostate cancer from benign prostatic hyperplasia in which the method includes determining the amount of [-1]pPSA, [-2]pPSA, [-3]pPSA [-4]pPSA. [-5]pPSA. [-6]pPSA and [-7]pPSA in a sample, wherein said determination does not use antibodies that display significant binding to the mature form of PSA.
  • the ratio of the amount of proPSA to total PSA in a sample could also be determined by the methods described herein.
  • AV12-664 (ATCC CRL 9595), cultured in DMEM (high glucose) and 10% fetal clone (HyClone Logan, UT USA), were transfected with pGTD-PSA using Lipofectamine (Life Technologies, Inc (Gibco BRL), Rockville, MD, USA.). Transfected. AV12-664 cells (AV12-PSA) were selected in 400 nM methotrexate (Sigma Chemical Company St Louis, MO, USA). AV 12-664 transfected with the empty vector (AV 12-PGTD) were also selected in a similar manner for use as negative control. Single cell clones were isolated. Viability of cells was assessed by trypan blue dye exclusion.
  • Murine mAbs PSM 773 and HKIG 586.1 were used.
  • PSM 773 is one of the components of Tandem®-MP PSA kit (Hybritech Incorporated, San Diego, CA, USA) and has been shown to be specific for PSA ( Wang, T.J. et al., Analysis of cross-reactivity of anti-PSA monoclonal antibodies with recombinant human glandular kallikrein, J. Urol., 155:695A, 1996 ).
  • HK1G 586.1 is an anti-hK2 antibody. Kumar A. et al., Cancer Research, 56:5397-5402, 1996 .
  • Serum containing spent media from AV12-PSA cells was collected on specified days.
  • PSA was measured using Tandem®-MP PSA and free PSA assays (both from Hybritech Incorporated, San Diego, CA, USA) according to manufacturer's instructions. Spent media from AV12 and AV 12-PGTD cells were used as negative controls.
  • tissue culture flasks containing AV12-PSA cells were grown to approximately 60-70% confluency, washed with PBS and serum free HH4 media was added.
  • Spent media harvested on specified days was concentrated using a Centricon 10 (Amicon, Inc, Beverly, MA, USA), incubated with either purified trypsin or purified hK2 followed by ACT and subjected to SDS-PAGE on a 4-20% gel (Bio-Rad, Inc, Hercules, CA, USA). After electrophoresis, proteins were electroblotted onto nitrocellulose membranes.
  • Primary antibodies (1-10 ⁇ g/ml) and secondary antibodies (goat anti-mouse IgG-horseradish peroxidase, 1:500; Jackson Immunosearch Laboratories, Inc, West Grove, PA, USA) were used to probe the blots.
  • the immunoreactive signals were detected using the enhanced chemiluminescence (Amersham, Buckinghamshire, England, United Kingdom) system according to the manufacturer's instructions.
  • mAb PSM 773 was coupled to AminoLink (Pierce Biotechnology Rockford. IL, USA) according to the manufacturer's instructions. Tissue culture flasks containing AV 12-PSA cells were grown to approximately 60-70% confluency, washed with PBS and serum free HH4 media was added. Spent media was harvested on specified days, concentrated and incubated with the above resin overnight at 4°C with stirring. The resin was then made into a column, washed with PBS and the PSA was eluted with 100 mM glycine, 0.5 M NaCl, pH 2.5. The samples were immediately neutralized with 1 M TRIS, pH 8.0.
  • Enzymatic activity of PSA was measured according to the procedure published by Christensson, A. et al., Enzymatic activity of prostate-specific antigen and its reactions with extracellular serine proteinase inhibitors, Eur. J. Biochem., 194:755-763, 1990 .
  • PSA preparations (either purified from seminal fluid or day 7 spent media of AV 12-PSA#8 cells) were incubated with 1 mM pNA-derivatized peptide chromogenic substrates (methoxysuccinyl-Arg-Pro-Tyr-pNA, S2586; Pharmacia Hepar, Inc, Franklin, OH, USA) in 200 mM TRIS 5 mM EDTA (pH 8.0) at 37°C.
  • the enzymatic activity of PSA was determined by hydrolysis of the peptide chromogenic substrates, leading to an increase in absorbance at 405 nm.
  • hK2 Purified pPSA (4.7 ⁇ M) was incubated with purified hK2 (0.56 ⁇ M) at 37°C in 100 mM TRIS 2 mM EDTA, pH 8.
  • Affinity purification of hK2 is described by Kumar, A. et al., Expression of human glandular kallikrein, hK2, in mammalian cells, Cancer Res. 56:5397-5402, 1996 and Mikolajczyk, S.D. et al., Human glandular kallikrein (hK2) shows arginine-restricted specificity and forms complexes with plasma protease inhibitors, Prostate 34:44-50, 1998 .
  • HIC column specifications and buffer compositions were as follows: polypropylaspartamide column, 4.6 X 250 mm, PolyLC (distributed by Western Analytical, Temecula, CA, USA), Buffer A: 1.2 M sodium sulfate, 50 mM sodium phosphate, pH 6.3; Buffer B: 50 mM sodium phosphate, 5% v/v 2-propanol, pH 7.3.
  • the cDNA for PSA was cloned into the pGT-d vector under the control of the GBMT promoter using an approach similar to the one described for hK2 by Kumar A. et al., Cancer Res. 56:5397-5402, 1996 .
  • AV12 cells were transfected with the pGTD-PSA expression vector. Cells were selected in 400 nM methotrexate for 2-3 weeks, and single cell clones were analyzed for PSA expression using Tandem®-MP PSA assay and on Western blots using mAb PSM 773. Clone AV12-PSA#8 was selected based on its high expression levels of a PSA-immunoreactive band at ⁇ 32 kDa.
  • the spent media from AV12-PSA#8 cells was collected and concentrated.
  • the PSA in the media was purified by affinity chromatography using PSM 773, a PSA-specific mAb.
  • N-terminal sequencing analysis of the purified protein revealed the sequence: APLILSRIVGG. This sequence corresponds with the sequence predicted for the terminus of proPSA that starts with -7 aa. Another species starting at -5 aa (leu) was also identified. No competing sequence corresponding to the mature form of PSA was evident from the profile of aa released sequentially by the Edman degradation procedure.
  • proPSA expressed by AV12-PSA#8 is enzymatically inactive and can be converted to enzymatically active PSA by mild trypsin treatment
  • a spectrophotometric assay was employed using the commercially available chromogenic substrate, methoxysuccinyl-Arg-Pro-Tyr-pNA (S-2586).
  • hK2 is another member of human kallikrein family. It is predominantly expressed in the prostate epithelium, the site where PSA is also abundantly expressed. hK2 exhibits arginine restricted trypsin-like activity.
  • purified hK2 was added to the spent media of AV12-PSA#8 cells. After 60 minutes of incubation at 37°C, ACT was added to these samples. After another 4 hours of incubation at 37°C, the reaction was stopped by addition of sample buffer+ ⁇ ME and boiling. The samples were then electrophoresed, electroblotted and probed with PSM773 ( Figure 3 ).
  • FIG. 4 shows the mixture of hK2 and pPSA at time 0 and Figure 4B shows the same mixture after a 2 hour incubation at 37°C.
  • the retention times for hK2 (peak 1) and pPSA (peak 2) were identical to that of purified hK2 and pPSA, respectively when injected separately (data not shown).
  • the hK2 converted PSA contained enzymatic activity of 58 nmoles/minute/mg on S-2586 substrate. This value was comparable to the enzymatic activity of PSA purified from seminal fluid on the same substrate. In contrast the pPSA sample prior to hK2 treatment contained ⁇ 5% of the PSA enzymatic activity. Purified pPSA when incubated without hK2 showed no conversion to PSA (data not shown).
  • PSA is translated as an inactive preproPSA precursor.
  • the signal peptide After passage through the secretory pathway, the signal peptide is cleaved, yielding the pro form of the protein.
  • the pro peptides are generally cleaved inside the cell (e.g., tissue plasminogen activator, protein C and tumor necrosis factor), there are exceptions (e.g., renin, trypsin, chymotrypsin and hK2) that are secreted as pro proteins and cleaved extracellularly ( Kumar. A. et al., Cancer Res. 56: 5397-5402, 1996 ).
  • PSA is secreted as proPSA from the mammalian cells: (a) spent media of AV 12-PSA#8 cells had no PSA-like enzymatic activity, (b) the PSA form in the spent media of AV12-PSA#8 cells did not complex with ACT as demonstrated by Western blot analysis, (c) trypsin treatment of spent media of AV 12-PSA#8 resulted in nature PSA that was enzymatically active and formed a complex with ACT, and (d) purification and sequence analysis of the PSA form present in the spent media of AV12-PSA#8 confirmed its identity as proPSA.
  • PSA exists in many forms in SF and in serum. These forms include complexes of PSA with protease inhibitors such as ACT and Protein C Inhibitor (PCI) PSA also exists as a PSA-MG PSA-alpha 2 macroglobulin complex and free PSA. It is possible that some of the free PSA in the serum and SF is in fact proPSA. Our data suggest that proPSA exists in biological fluids and may be a useful marker for prostatic diseases.
  • protease inhibitors such as ACT and Protein C Inhibitor (PCI)
  • PCI Protein C Inhibitor
  • hK2 another member of human kallikrein family, exhibits arginine-restricted trypsin-like activity and similar to PSA, it is predominantly expressed in the prostate epithelium (Morris, B.J. supra; Chapdelaine, P., supra ).
  • hK2 is secreted as prohK2 by mammalian cells.
  • prohK2 is converted to enzymatically active hK2 extracellularly.
  • hK2 has been shown to possess autocatalytic activity as it can clip itself between residues -1-+1. Mikolajczyk, et al., Alanine 217 is important for the catalytic function and autoactivation of prostate-specific human kallikrein 2 . Eur. J. Biochem 246: 440-446, 1997 .
  • hK2 may be regulating PSA activity and complex formation with protease inhibitors by clipping at some of the above-mentioned sites.
  • PSA may also be regulating hK2 activity by clipping hK2 at chymotrypsin sensitive sites. The reagents described herein plus hK2 expressed in mammalian cells should facilitate these experiments.
  • pPSA is present in human serum.
  • PSA is secreted as the pPSA form in human tissue and it is converted to mature PSA extracellularly.
  • pPSA is stable in human serum and thus may be a useful diagnostic marker for prostate cancer (pCa) or BPH.
  • pCa prostate cancer
  • We evaluated the presence of pPSA in human serum by first using affinity purification to purify all forms of PSA present in a pool of human serum.
  • the affinity column was washed with 50 mls of PBS and the PSA eluted with 3 X 1 ml volumes of 100 mM glycine, 0.5 M sodium chloride, pH 2.5.
  • the eluant (3 mis) was neutralized with 300 ⁇ l of 1 M TRIS, pH 8.
  • Ammonium sulfate was added to the eluant to a final concentration of 2 M and this sample was applied to an HPLC column to be resolved by hydrophobic interaction chromatography (PolyLC, polypropyl aspartamide column, 1000 A pore size, 4.6 mm X 200 mm distributed by Western Analytical, Temecula, CA USA).
  • Buffer A was 20 mM sodium phosphate, 1.2 M sodium sulfate, pH 6.3 and Buffer B was 50 mM sodium phosphate, 5% 2-propanol, pH 7.4.
  • the elution gradient was 0-35% B from 0-1 minute and 35-80% B from 1-14 minutes, before re-equilibration in Buffer A.
  • the flow rate was 1 ml/minute.
  • Figure 5 shows the retention times (RT) of standards resolved under the HIC chromatographic conditions described above.
  • Figure 5A shows the RT of active ACT.
  • Figure 5B shows the RT of active ACT incubated with PSA purified from seminal fluid. Because seminal fluid PSA is known to contain approximately 50% inactive PSA (known as "free" PSA because it will not complex with ACT), incubation of PSA with ACT results in PSA-ACT as well as free PSA. PSA also clips and inactivates ACT and so inactive ACT (iACT) is also seen.
  • Figure 5C shows the RT of seminal fluid PSA. There is no difference between the retention times of active PSA and inactive PSA under these chromatographic conditions.
  • Figure 6A shows the RT of standards of the different forms of PSA. All forms were verified by amino acid sequencing. The [-7,-5]pPSA peak contains approximately equal levels of [-7]pPSA and [-5]pPSA forms which are not resolved from each other.
  • Figure 6B shows the profile of PSA forms from serum bound to the PSM773 affinity column as described above. Samples were collected in 0.5 ml fractions and assayed by Tandem ® -MP free PSA assay (fPSA assay, Hybritech Incorporated, San Diego, CA, USA.). The fPSA assay detects both pPSA and free (inactive) PSA.
  • Tandem ® -MP free PSA assay fPSA assay, Hybritech Incorporated, San Diego, CA, USA.
  • the minor peak at 7 minutes is due to the slight cross-reactivity of the fPSA assay to the PSA-ACT eluted from the affinity column.
  • the actual level of PSA-ACT in this sample is about 10 times higher than the level of free PSA (data not shown).
  • the peaks at 10 minutes and 12 minutes correspond to mature PSA and [-4]pPSA, respectively.
  • the anti-PSA monoclonal antibody detects a major band at approximately 90 kDa which represents PSA-ACT in all three serum specimens, as shown in Figure 8 .
  • a minor band at approximately 33 kDa is also detected in two of the three serum specimens.
  • This lower molecular weight form of PSA represents an inactive uncomplexed form of PSA since active PSA would be readily complexed with ACT.
  • the presence of the 33 kDa form of PSA in the serum samples with higher PSA levels probably is a reflection of the sensitivity of the method and antibody.

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EP98918814A 1997-04-30 1998-04-28 Forms of prostate specific antigen and methods for their detection Expired - Lifetime EP0981629B1 (en)

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US84640897A 1997-04-30 1997-04-30
US846408 1997-04-30
PCT/US1998/008498 WO1998049323A1 (en) 1997-04-30 1998-04-28 Forms of prostate specific antigen and methods for their detection

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EP0981629A1 EP0981629A1 (en) 2000-03-01
EP0981629B1 true EP0981629B1 (en) 2008-08-13

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JP (1) JP5284554B2 (ja)
AT (1) ATE404676T1 (ja)
AU (1) AU739546B2 (ja)
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US7659073B2 (en) 1997-04-30 2010-02-09 Hybritech Incorporated Forms of prostate specific antigens and methods for their detection
US7288636B2 (en) 1997-04-30 2007-10-30 Hybritech Incorporated Forms of prostate specific antigens and methods for their detection
US6300088B1 (en) * 1997-11-24 2001-10-09 Duke University Method of detecting prostate specific antigen
CA2360073C (en) 1999-01-28 2011-01-18 Gen-Probe Incorporated Probes and primers for detecting prostate specific antigen (psa) in a biological sample
US6423503B1 (en) * 1999-04-30 2002-07-23 Hybritech Incorporated Forms of free prostate-specific antigen (PSA) and their association with prostate tissues from prostate peripheral zone and transition zone
US20030219840A1 (en) * 2002-05-24 2003-11-27 Mikolajczyk Stephen D. Method of analyzing proenzyme forms of prostate specific antigen in serum to improve prostate cancer detection
ES2277846T3 (es) * 1999-07-29 2007-08-01 Medarex, Inc. Anticuerpos monoclonales humanos para antigeno prostatico especifico.
FR2807438B1 (fr) * 2000-04-10 2004-09-17 Bio Merieux Nouveaux anticorps reconnaissant specifiquement le psa libre inactif, et leurs applications
ATE335765T1 (de) * 2000-05-24 2006-09-15 Hoffmann La Roche Antikörper gegen spezielle formen des propsa und deren verwendung in immunoassays
FI20002127A0 (fi) * 2000-09-27 2000-09-27 Artic Partners Oy Ab Uusi vasta-aine, immunomääritys ja menetelmä eturauhassyövän havaitsemiseksi
CN113237162B (zh) * 2021-05-28 2022-12-27 西安建筑科技大学 一种冷冻水循环***控制优化方法、***及设备

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JPH08502889A (ja) * 1992-10-29 1996-04-02 トーマス・ジェファーソン・ユニバーシティ 前立腺癌の微小転移を検出する方法
US6103237A (en) * 1993-07-22 2000-08-15 Hybritech Incorporated Stable variant hK2 polypeptide
EP0725139A3 (en) * 1995-02-03 1997-11-26 Bayer Corporation Recombinant prostate-specific antigen and its use as an immunoassay calibrator
CA2218754A1 (en) * 1996-11-15 1998-05-15 Eli Lilly And Company Recombinant psa expression vectors and assays using the same

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CA2286090C (en) 2013-01-08
JP5284554B2 (ja) 2013-09-11
DE69839876D1 (de) 2008-09-25
EP0981629A1 (en) 2000-03-01
CA2286090A1 (en) 1998-11-05
AU7166898A (en) 1998-11-24
JP2002501384A (ja) 2002-01-15
ATE404676T1 (de) 2008-08-15
AU739546B2 (en) 2001-10-18
WO1998049323A1 (en) 1998-11-05
ES2312186T3 (es) 2009-02-16

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